Noise Reduction and Comfort Noise Gain Control Using Bark Band Weiner Filter and Linear Attenuation

1. In a telephone having an audio processing circuit including an analysis circuit for dividing a audio signal into a plurality of frames, each frame containing a plurality of samples, a noise suppression circuit, and a noise reduction circuit, the improvement comprising: means for detecting long non-speech intervals; and means for switching to noise reduction from noise suppression when a long, non-speech interval is detected.

2. The telephone as set forth in claim 1 and further comprising: a gain smoothing filter in said noise reduction circuit, wherein said gain smoothing filter has a long time constant when switching to noise reduction from noise suppression to provide a gradual transition from one level of gain to another.

3. The telephone as set forth in claim 2 wherein said filter has a short time constant during short non-speech intervals.

4. The telephone as set forth in claim 1 wherein said means for detecting is coupled to the output of said noise suppression circuit, thereby improving the performance of the means for detecting at low signal to noise ratio.

5. In a telephone including a noise suppression circuit having a circuit for estimating background noise and having a comfort noise generator coupled to said noise suppression circuit for generating comfort noise based on data from said circuit for estimating background noise, the improvement comprising: means for detecting long non-speech intervals; and means coupled to said circuit for postponing an estimate when said means for detecting long non-speech intervals detects a long non-speech interval.

6. In the telephone as set forth in claim 5 , wherein said telephone further includes spectral gain calculation circuitry and said improvement further comprises: means for adjusting the gain of the comfort noise based upon data from said spectral gain calculation circuitry.

7. The telephone as set forth in claim 6 wherein said data is averaged.

8. The telephone as set forth in claim 5 wherein said means for detecting is coupled to the output of said noise suppression circuit, thereby improving the performance of the means for detecting at low signal to noise ratio.